Most support bearings present an inside wall that is cylindrical. Such support bearings are entirely suitable so long as the bending stiffness of the cylindrical element and/or the load to which the cylindrical element is subjected lead to deformation of the cylindrical element that is negligible relative to the macroscopic dimensions of the support bearing.
When the cylindrical element is more flexible, or when it is subjected to higher loading, the deformation of the cylindrical element is no longer negligible and the cylindrical element then comes to bear against the support bearing in one or more zones of small area, thereby considerably increasing the pressure that is applied locally to the cylindrical element. Under such conditions, the cylindrical element bears on the end of the support bearing, which gives rise to marking on the cylindrical element due to deterioration of its surface coating. This phenomenon leads to a degraded surface state for the cylindrical element which can give rise to the initiation of fatigue cracks.
To solve this problem, proposals have already been made for support bearings having cylindrical inside walls that present chamfers at at least one of the ends of each inside wall. Such support bearings provide a certain amount of improvement over support bearings having inside walls that are purely cylindrical.
Proposals have also been made to give the inside wall of the support bearing a surface that is not cylindrical, but that bulges.
Various types of surface have been considered, and formulae have been proposed for determining the parameters of such surfaces as a function of geometrical data as the height of the support bearing or the diameter of the cylindrical element.
Those formulae have the drawback of taking no account of the stiffness characteristics of the cylindrical element or of the loading actually applied thereto.
To fill out the technical background, reference may be made to U.S. Pat. Nos. 4,396,170, 3,969,029, 4,136,582, and 4,688,808.